Why is Shia LaBeouf Dancing Around in his Undies? [VIDEO]

Oh, Shia LaBeouf! He's become more well known for his craziness lately, than his movies. He was caught dancing in his undies, but it's not what you think! Check out the latest video from SIA's new single "Elastic Heart," He's staring with Maddie Ziegler (Dance Moms) who starred in Sia's other epic video for the song "Chandelier."  The video is well... take a look and see what you think....

And here's the Chandelier video. That Maddie can dance!